Polarization of Light

Explore how light is polarized in a single plane by a polarizer and how that plane-polarized light must be oriented at a specific angle to pass through a second polarizer. To get a better understanding of the configuration presented in this tutorial, use the mouse cursor to reposition the light waves and polarizers to suit your tastes. To do this, place the cursor anywhere in the applet window, hold down the left mouse button, and roll the mouse around the screen. The light waves will follow.

Light is traveling from left to right when the applet first initializes. Unpolarized white light is represented on the left-hand side of the window before the first polarizer by a set three sine waves that are colored red, green, and blue. These light waves are rotating about the propagation axis to represent that the fact that white light is vibrating in all planes perpendicular to the direction of propagation. Use the slider on the left to rotate the first polarizer. As the polarizer rotates, it changes the angle of the plane of light passed by the polarizer. Try this first.

Light that is parallel to the computer monitor screen surface is represented by a flat sine wave. Light that is perpendicular to the screen surface is represented by a solid straight line. Light at any other angle is represented by a sine wave of lesser amplitude than that which is parallel to the monitor. When the second polarizer is parallel to the first polarizer, all light passing through the first polarizer also passes through the second. As the second polarizer is rotated through a 90-degree angle, the intensity of light decreases until it is totally blocked when the two polarizers are positioned at right angles with respect to one another.